Fuels containing deposit control additives



Patented July 22, 1958 y ce FUELS CONTAINING DEPOSIT CONTROL ADDITIVESNo Drawing. Application Fehruary 24, 1956 Serial No. 567,445

9 Claims. 01. 44-70 This invention relates to hydrocarbon fuelscontaining a novelclass of additives which reduce the depositformingtendency of hydrocarbon fuels. More specifically, this inventiondisclosed that superior motor fuels are obtained by the addition of aminor amount of a polymethylene glycol bis(glycol ether carbonate) ofprescribed composition. 7 As automobile manufacturers anually raise thecompression ratio oftheir automobile engines in the race for higherhorsepower, the need becomes greater for gasolines which burn cleanly,that is, have low deposit-forming tendencies. Engine deposits which findtheir origin in the fuel are primarily responsible for surface ignitionphenomena such as preignition and octane requirement increase (ORI)which is the tendency of spark ignition engines in service to requirehigher octane fuels for proper performance. As a consequence, gasolinemanufacturers have placed increasing stress on reducing thedepositforming tendencies of their fuels and have resorted to variousadditives either to reduce the amount of deposits or to minimize theireffects. The present invention involves the discovery that a particularclass of polymethylene glycol derivatives are outstanding in controllingthe deposit-forming tendencies of hydrocarbon fuels.

In our copending application, Serial No. 567,476 filed of even datethere are disclosed novel polymethylene glycol carbonates of the generalformula wherein R is a divalent symmetrical polymethylene .radicalcontaining at least 4 carbon atoms, R. is an aliphatic hydrocarbonradical containing 1 to 12 carbon atoms and n has a value of 0 to 10.This invention involves the discovery that a particular group of thesenovel compounds, namely the polymethylene glycol bis (glycol ethercarbonates) are deposit control fuel additives.

The improved hydrocarbon fuels ofthis invention containa polymethyleneglycol bis(glycol ether carbonate) of the general formula RQ (CH CH OOCOROCO OCH CH ,OR'

wherein R is a divalent symmetrical polymethylene vradical containing atleast 4 carbon, atoms and preferably 4 to 12 carbon atoms, R is analiphatic hydrocarbon radical containing 1 to 12 carbon atoms and n hasa value of 1 to 6. The polymethylene glycol bis(glycol ether carbonates)prescribed in this invention are effective deposit-control additives inconcentrations as low asf0.0l volume percent, but concentrations of 0.04to 0.3 volume percent are normally employed. There is no critical upperlimit of concentration but economic considerations dictate thatconcentrations 'less than'lO volume percent glycol carbonate ester bepresent in the fuel.

The polymethylene glycol bis(glycol ether' carbonates) which inhibit thedeposit-forming tendencies of hydrocarbon fuels are readily prepared bythe series of reactions described in the aforeidentified copendingapplication. In general, the preparation involves the formation of achloroformate by. reaction of phosgene with an ethylene or polyethyleneglycol monoalkyl ether and subsequent reaction of the chloroformate witha polymethylene glycol in the presence of a hydrogen chloride acceptorsuch as pyridine or quinoline. An alternate reaction procedure involvesformation of a dichloroformate by reaction of a polymethylene glycolwith phosgene and subsequent reaction of the dichloroformate with amonoether of ethylene or polyethylene glycol in the presence of ahydrogen chloride acceptor.

The hydrocarbon fuels of this invention are characterized by lowdeposit-forming tendencies with the result that an engine operatedtherewith shows exceptionally clean intake system, combustion space,valves, ring belt area and injection system of a diesel engine. The lowdeposit level in the engine minimizes surface ignition in all itsmanifestations, mainly preignition and knock. In addtion, the lowdeposit level reduces the engines octane requirement increase. Depositson surfaces contacted by the lubricating oil, such as piston skirts andcylinder walls, are very markedly reduced.

The polymethylene glycol bis(glycol ether carbonates) usable in thefuels of the invention are exemplified by the following: tetrarnethyleneglycol bis(butoxyethyl carbonate), pentamethylene glycolbis(methoxyethyl carbonate), hexamethylene glycol bis(ethoxyethylcarbonate), hexamethylene glycol bis(propoxyethylcarbonate),hexamethylene glycol bis (butoxyethoxyethyl carbonate), pentamethyleneglycol bis(methoxyethoxyethyl carbonate), octamethylene glycolbis(ethoxyethoxyethyl carbonate), octarnethylene glycolbis(methoxyethoxyethyl carbonate), decamethylene glycolbis(ethoxyethoxyethyl carbonate), decamethylene glycolbis(butoxyethoxyethyl carbonate), pentamethylene glycolbis(2-butene-l-oxyethyl carbonate), tetramethylene glycolbis(methoxyethoxyethyl carbonate), tetramethylene glycolbis(ethoXyethoxyethyl carbonate), pentamethylene glycol bis(bu-ltoxyethoxyethyl carbonate), pentamethylene glycol bis-(octoxyethoxyethyl carbonate), pentamethylene glycol bis(pentoxyethylcarbonate), heptamethylene glycol bis-' for proper .functioning as afuel additive. An additive with high water solubility is generally lostfrom a hydrocarbon fuel during storage which is usually over water.

The polymethylene glycol bis(glycol ether carbonates) effective inreducing deposit formation in hydrocarbon fuelsare all characterized byboiling points above 650 F., a molecular weight above 300 and a carbonto oxygen weight ratio below 2.5. Apparently, the glycol carbonate estermust possess all of these properties simultaneously in order to impartdeposit-forming properties to hydrocarbon fuels.

In summary, the following conclusions can be made as to the requirementsof each section of the additive molecule for the production of apolymethylene glycol carbonate ester derivatives are ineffective asdeposit-con VI trol additives. '(4) Terminal aliphatic radicals contain1 to 12 carbon atoms with aliphatic radicals containing 2 to 6 carbonatoms being preferred.

The polymethylene glycol bis(glycol ether carbonates)" are effective asdeposit-control additives in concentrations" "between 0.01 and 1.0volume percent of thefuel. Gen

erally, dirtier fuels having a high concentration of olefinic componentsrequire high concentrations of the additive whereas cleaner burningpremium fuels are improved with respect to deposit-formingcharacteristics by smaller concentrations of the polymethylene glycolbis (glycol ether carbonate) ester. In general, dirtier gasolin'esrequire an additive concentration between 0.1 and 0.3 volume percentwhereas clean-burning premium fuels only need an additive concentrationbetween 0.01 and 0.08 volume percent." As indicated previously, there isno critical upper limit from a functional viewpoint but economicsdictate that the glycoladditive be less than 1 volume percent.

The polymethylene glycol bis(glycol ether carbonates) of the typedescribed in this invention are effective in controlling deposits inhydrocarbon fuels having boiling points up to about 700 F., althoughbenefits also result when polymethylene glycol bis(glycol ethercarbon-ates) are added to fuels containing residual stocks of higherboiling point. The major application of the additive is in gasoline forautomotive engines wherein fuel-derived engirie deposits have become aparticularly vexing problem. The deposit-forming properties of dieselfuels and fuels designed for use in jets and gas turbines are alsoimproved by the polymethylene glycol derivatives of this invention. Indiesel fuels the presence of the additive maintains the injection systemand combustion zone in a clean condition. This is particularly importantwith the increasing use of the so-called economy diesel fuels, that isfuels having a high sulfur content or containing cracked or residualstocks. Polymethylene glycol bis(glycol ether carbonates) findparticular application in jet fuels used as a cooling medium prior totheir consumption. A polymethylene glycol bis(glycol ethercarbonate)-containing jet fuel is an excellent heat exchange mediumsince it is relatively free from deposits in the cooling system andburner nozzle where deposits cannot be tolerated.

The deposit-forming properties of both regular and premium gasolines,both of the leaded and of the nonleaded type, are improved by theaddition of polymethylene glycol bis(glycol ether carbonates). Thegasolines to which the polyglycol carbonate esters are added can bebroadly defined as hydrocarbon fuels having boiling points up toapproximately 400 F.

The action of the additives in controlling the depositforming tendenciesof motor fuel was demonstrated by a Modified Chevrolet Deposits TestCRCFL2650.

The laboratory engines are operated under the standard conditions ofthis test with the exception that crankcase oil temperatures were 10 F.lower, the water jacket tempe ratures were 5 F. lower, and thecrankcases of the test engines were ventilated. These modifications arein every case in the direction of making the test more severe and areintended to simulate low temperature conditions wherein depositformation is most pronounced. After the termination of each run, theengine is disassembled and its parts are evaluated by a merit systemadapted from the CRCL-4l252 test. This, merit system involves visualexamination of the engine part in question and their rating according todeposits by comparison with standards which have assigned ratings. Forexample, a rating of 10. on piston skirt designates a perfectly cleanpiston While a rating of zero represents the worst condition. Similarly,a rating of 100 on total engine deposits represents a perfectly cleanengine, etc.

In the following table there are shown the depositcontrol properties ofpolymethylene glycol bis( glycol ether carbonates) in comparison withthose of polymethylene glycol bis(alkyl carbonates). Base fuels A and Bare high quality regular grade gasolines comprising a mixture thermalcracked stock, fluid catalytically cracking and straight run gasoline.Base fuel A has an 87.0 AST M research octane rating containing 2.90 ml.of TEL per gallon, had an API gravity of 58.0-and a boiling rangebetween106 and 396 F.; it was negative in. the,

copper strip corrosion test and had an oxidation stability in the ASTMtest of 530 minutes minimum. Base fuel B had a 90.5 ASTM research octanerating, contained 2.67 ml. of TEL per gallon, had an API gravity of 59.0and a boiling range between 93 and 395 F.; it was negative in the copperstrip corrosion test and had an oxidation stability of 445 minutesminimum. The reference fuels also contained minor amounts of gasolineinhibitors, namely N,N'-di-secondary butyl paraphenylene diamine,lecithin, and N,N-disalicylidene-LZ-diaminopropane. In all runs, thelaboratory engines in the Chevrolet S-II test were lubricated withAdvanced Custom Made Havoline, a heavy duty type oil meeting SupplementI requirements and Manufactured by The Texas Company.

' Piston Total Skirt Engine Deposits Base Fuel A 4. 7 77. 7 Base Fuel Aplus 0.1 vol. percent of:

1,5-pentamethylene glycol bis (2-ethoxyethyl carbonate) 7. 8 82. 81,5-pentamethylene glycol bis(Z-ethylhexyl carbonate) 4. 7 70. 7 BaseFuel B 6. 1 79. 9 Base Fuel B plus 0.1 vol. percent of:

1,5-pentamethylene glycol bis(2,2,2"-triethoxyethyl carbonate) 9. 7 90.7 1,5-pentamethylene glycol bis(n-amyl carbonate) 4. 8 76. 8

The fuels formed by the addition of the polymethylene glycol bis(glycolether carbonates) to a regular grade gasoline are equivalent to somepremium grade gasolines from the standpoint of engine cleanliness. Thepiston skirt ratings of 7.8 to 9.7 and total engine ratings of 82.8 to90.7 are better ratings than are obtained with some premium fuels. Theability of the polymethyleneglycolbis (glycol ether carbonates) to raiseregular grade fuels to the engine cleanliness level of premium gradefuels is a substantial step forward in solving the surface ignitionproblems encountered in high compression engines.

It is significant that the polymethylene glycol bis(alkyl carbonates),which are also disclosed in Serial No. 567,- 476 filed of even date, areineffective and, in some respects, deleterious deposit controladditives. It has been theorized that the ether linkage in thepolymethylene glycol bis(glycol ether carbonates) is necessary for theadditive to solubilize the low temperature deposits. Whatever theexplanation of the elfectiveness of polymethylene glycol bis(glycolether carbonates) and of the ineffectiveness of polymethylene glycolbis(alkyl carbonates) the results are striking.

An outstanding feature of the polymethylene glycol bis(glycol ethercarbonates) of this invention is that they do not possess anydeleterious eifect on other properties of the fuel. In many fueladditives, engine wear of parts such as piston rings, cylinder walls,bearings and valves, is a definite problem. Fuels containingpolymethylene glycol bis( glycol ether carbonate) of prescribedcomposition actually decrease engine wear under high temperatureconditions.

Obviously many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indicated in the appended claims.

We claim:

1. A normally liquid hydrocarbon fuel for internal combustion enginescontaining a polymethylene glycol bis( glycol ether carbonate) of thegeneral formula R'O CH CH O) OCOROCO( OCHQCH ,OR

wherein R is a divalent symmetrical polymethylene radical containing 4to 10 carbon atoms, R is an aliphatic hydrocarbon radical containing 1to 12 carbon atoms and n has a value of 1 to 6, said glycol derivativehaving a carbon to oxygen weight ratio below 2.5 being present in anamount sufficient to reduce the deposit-forming properties of said fuel.

2. A hydrocarbon fuel according to claim 1 containing 0.01 to 1.0 volumepercent of polymethylene glycol bis (glycol ether carbonate).

3. A hydrocarbon fuel according to claim 1 containing 0.04 to 0.3 volumepercent of polymethylene glycol bis( glycol ether carbonate).

4. A gasoline containing a polymethylene glycol bis (glycol ethercarbonate) of the general formula wherein R is a divalent symmetricalpolymethylene radical containing 4 to 10 carbon atoms, R is an aliphatichydrocarbon radical containing 1 to 12 carbon atoms and n has a value of1 to 6 said glycol derivative having a carbon to oxygen weight ratiobelow 2.5 and being present in an amount suflicient to reduce thedeposit-forming properties of said-gasoline.

5. A gasoline according to claim 4 containing 0.01

6 to 1.0 volume percent of polymethylene glycol bis(glycol ethercarbonate).

6. A gasoline according to claim 4 containing 0.04 to 0.3 volume percentofpolymethylene glycol bis(glycol ether carbonate).

7. A gasoline according to claim 4 in which said polymethylene glycolbis( glycol ether carbonate) has terminal aliphatic radicals containing3 to 10 carbon atoms and said It has a value of 1 to 2.

8. A gasoline containing 0.01 to 1.0 volume percent 1,5-pentamethyleneglycol bis(Z-ethoxyethyl carbonate).

9. A gasoline containing 0.01 to 1.0 volume percent 1,5-pentamethyleneglycol bis(2,2',2-triethoxyethyl carbonate).

References Cited in the file of this patent UNITED STATES PATENTS2,331,386 Gaylor Oct. 12, 1943 2,379,252 Muskat et al June 26, 19452,651,657 Mikeska et a1. Sept. 8, 1953 2,789,891 Brandes et al. Apr. 23,1957

1. A NORMALLY LIQUID HYDROCARBON FUEL FOR INTERNAL COMBUSTION ENGINESCONTAINING A POLYMETHYLENE GLYCOL BIS(GLYCOL ETHER CARBONATE) OF THEGENERAL FORMULA